1. Field of the Invention
The present invention relates to a vapor deposition system adopted for manufacturing semiconductors, and particularly to a vapor deposition system having improved reliability and safety.
2. Description of the Prior Art
FIG. 1 shows an example of conventional vapor deposition system for depositing compound semiconductor material on a substrate to form a compound semiconductor file on the substrate.
In the figure, the system comprises a reactor tube 100, a reactor chamber 101 formed inside the reactor tube 100, a susceptor 103 on which a substrate 102 is placed, and a support rod 104 for removably supporting the susceptor 103. The support rod 104 is movably inserted into the reactor tube 100 which is kept airtight by a bellows 105 attached to the bottom of the reactor tube 100. The support rod 104 is moved vertically by a raiser 116.
The reactor tube 100 comprises an upper part 100a made of glass and a lower part 100b made of metal. The upper and lower parts 100a and 100b are airtightly connected to each other at flange portions 100c through an O-ring 106. The upper part 100a has an inlet 100d for supplying gases such as material gases, carrier gases and inert gases into the reactor chamber 101. The lower part 100b has an exhaust port 100e for discharging non-reacted gases from the reactor chamber 101 and adjusting a pressure of the reactor chamber 101. A high-frequency coil 107 is disposed around the reactor chamber 101 to heat the same.
A preparatory chamber 109 is formed beside the lower part 100b of the reactor tube 100. The preparatory chamber 109 can communicate with the reactor chamber 101 through a gate valve 108. In the preparatory chamber 109, a susceptor receptor receiver 110 is movable in the direction of an arrow mark A. The susceptor receiver 110 is connected to a moving rod 112, which is connected to a mover 115. A bellows 111 maintains airtightness between the preparatory chamber 109 and the moving rod 112.
The susceptor receiver 110 is moved by the moving rod 112 and mover 115 into the reactor chamber 101 through the gate valve 108, thereby bringing a susceptor placed on the susceptor receiver 110 from the preparatory chamber 109 to the support rod 104 as well as bringing them from the support rod 104 into the preparatory chamber 109.
A lid 114 is removably arranged on the preparatory chamber 109 through an O-ring 113. An exhaust port 109a is formed on the bottom of the preparatory chamber 109 to discharge non-reacted gases from the preparatory chamber 109 and adjust an internal pressure thereof.
To position the substrate 102 in the reactor chamber 101, the gate valve 108 between the reactor chamber 101 and the preparatory chamber 109 is firstly closed, and the lid 114 of the preparatory chamber 109 is opened. Thereafter, the substrate 102 is put on the susceptor 103 that has been positioned on the susceptor receiver 110 in advance. The lid 114 is closed, and the same gases (inert gases) as those supplied to the reactor chamber 101 are supplied to the preparatory chamber 109 through an inlet (not shown), thereby filling the preparatory chamber 109 and reactor chamber 101 with the same gases. A pressure of the preparatory chamber 109 is adjusted to be equal to that of the reactor chamber 101. The gate valve 108 is then opened, and the susceptor receiver 110 is moved by the mover 115 to the support rod 104 which has been brought to a lower position by the raiser 116 in advance. The susceptor 103 with the substrate 102 is transferred onto the support rod 104. Thereafter, the support rod 104 is raised by the raiser 116.
The susceptor receiver 110 is returned to the preparatory chamber 109 by the moving rod 112 and mover 115, and the gate valve 108 is closed. The high-frequency coil 107 is activated to heat the susceptor 103, thereby increasing a temperature of the substrate 102 to a predetermined value. Material gases such as arsine (AsH.sub.3), trimethylgallium (TMG) and trimethylaluminum (TMA) and carrier gases such as H.sub.2 are supplied into the reactor chamber 101 through the inlet 100d. Consequently, a compound semiconductor film is deposited on the substrate 102.
To take the substrate 102 having the deposited compound semiconductor film out of the reactor chamber 101, the material and carrier gases, are stopped at first. Residual gases are discharged by a rotary pump (not shown) from the reactor chamber 101 through the exhaust port 100c. Inert gases are supplied into the reactor chamber 101 through the inlet 100d to set a pressure of the reactor chamber 101 to be equal to that of the preparatory chamber 109. The gate valve 108 is opened. The susceptor receiver 110 is moved by the moving rod 112 and mover 115, and positioned below the susceptor 103 and substrate 102 in the reactor chamber 101. The support rod 104 is lowered by the raiser 116 to transfer the susceptor 103 and substrate 102 to the susceptor receiver 110, which is then moved by the moving rod 112 and mover 115 to the preparator chamber 109. The gate valve 108 is closed, an the lid 114 is opened to pick up the substrate 102 from the susceptor 103 that is on the susceptor receiver 110.
The above conventional vapor deposition system has the following problems:
(a) Not all of the material gases supplied to the reaction chamber 101 necessarily contribute to form the compound semiconductor film on the substrate 102. A portion of the gases that did not contribute to the film deposition may form reactive products, which gather below the susceptor 103 and largely adhere to the gate valve 108 positioned beside the lower part of the reactor chamber 101. The adhered reactive products cause the gate valve 108 not to be closed completely, and a leak of the gases and reactive products occurs. The gases are usually harmful and flammable, and therefore, if the gases or reactive products escape from the reactor chamber 101 into the preparatory chamber 109 through the gate valve 108 during the deposition process or when the substrate 102 is taken out from the preparatory chamber 109, they may cause explosion, fire, damage to humans, etc. Moreover, since a breakage of the reactor tube 100 and a deterioration of the O-ring 106 will cause harmful gases to leak out of the reaction chamber, avoidance of such a result is highly desirable.
(b) The susceptor 103 and susceptor receiver 110 are moved in the direction A through the gate valve 108 between the reactor chamber 101 and the preparatory chamber 109. This enlarges the size of the system (including the mover 115) in the direction A. In addition, the gate valve 108 shall be sufficiently large to pass the susceptor receiver 110. This may greatly increase vibration of the gate valve 108 in opening and closing the same. The vibration will cause the reactive products adhered to an inner wall of the reactor tube 100 to drop on the substrate 102, thereby abnormally growing the film on the substrate 102.
(c) Since the susceptor receiver 110 can move only in the direction A, the susceptor 103 on the support rod 104 shall be moved vertically by the raiser 116. Namely, the support rod 104 shall be moved vertically to transfer the susceptor 103 between the support rod 104 and the susceptor receiver 110. This complicates the structure of the raiser 16 which is usually equipped with a mechanism for rotating the susceptor 103.
(d) The reactor tube 100 comprises the upper and lower parts 100a and 100b that are tightly fixed to each other by the flange portions 100c through the O-ring 106. When phosphorous gases such as phosphine gases are supplied to the reactor chamber 101, the gases will react with a very small amount of air penetrated through the flange portions 100c to form phosphoric acid, which will corrode the O-ring 106 and cause a leakage.